This invention relates to a novel family of phosphors which are activated with one or a combination of trivalent activator cations.
In Journal of Luminescence 3, 109 - 131 (1970), an article by G. Blasse et al describes a family of phosphors having a fergusonite-type (tetragonal) crystal structure and the empirical formula YTaO.sub.4 wherein a small percent of the Y is replaced with travelent activator cations. Such phosphors are disclosed to be cathodoluminescent and photoluminescent, emitting light in the ultraviolet and visible regions of the spectrum depending upon the excitation and the activator cations present.